The present application is directed to a rotary switch, and more particularly to a rotary switch which cooperates directly with printed wiring contacts carried by a printed circuit board.
Push button switches which cooperate directly with printed wiring contacts on a printed circuit board are known. A typical switch of this type employs a pair of closely spaced printed wiring contacts, which may have comb-like configurations and be interleaved but which are nevertheless electrically disconnected from one another. A plastic spacer sheet rests on the printed circuit board and is provided with an aperture through which the pair of wiring contacts is exposed. A plastic contactor sheet rests on the spacer sheet. A metallic contactor element is affixed to the contactor sheet at a position above the pair of wiring contacts. Normally the contactor element is spaced apart from the printed wiring contacts by approximately the thickness of the spacer sheet. However, when the contactor sheet is pressed in the region above the contactor element, the contactor sheet protrudes through the aperture in the spacer sheet and the contactor element bridges the pair of wiring contacts, thereby electrically connecting them. De-bouncing circuitry is typically employed on the printed circuit board to avoid contact bounce. When the pressure on the contactor sheet is released, it springs back to its original position due to the resilience of the plastic and thereby opens the switch.
In this application, the term "printed wiring contact" will be used to designate a portion of the printed wiring pattern on a PCB, and particularly that portion which comes selectively into contact with some other conductor and serves as a switch contact. The printed wiring pattern on the PCB normally also includes conductors for connecting the printed wiring contacts to circuit elements mounted on the PCB and further conductors for establishing the desired connections among the circuit elements.
In a variation on the typical push button switch described above, there is only one printed wiring contact on the printed circuit board, and printed wiring on the contactor sheet is connected to the contactor element. When the contactor sheet is depressed, the contactor element touches the printed wiring contact on the PCB to electrically connect the printed wiring contact to the printed wiring on the contactor sheet. In yet another known push button switch employing printed wiring contacts, a pair of spaced apart printed wiring contacts is again provided on the PCB. However, instead of both a spacer sheet and a contactor sheet, a single, molded contactor sheet is used. The molded contactor sheet rests directly against the PCB but has a blister portion above the printed wiring contacts. The contactor element is affixed to the contactor sheet at the center of the blister portion, and is normally spaced apart from the printed wiring contacts. However, the blister portion collapses when it is depressed, thereby moving the contactor element into electrical contact with the printed wiring contacts.
Push button switches with printed wiring contacts are far less expensive than push button switch assemblies which are mounted on a chassis with nuts or other hardware and electrically connected to a printed circuit board using individual wires. For this reason, push button switches with printed wiring contacts are used in a wide variety of products, ranging from pocket calculators to digital clocks and video cassette recorders. In particular, push button switches with printed wiring contacts are frequently used to set the time depicted on displays in clocks and VCR's. In relatively inexpensive products the time might be set using a single push button switch. The time depicted on the display is incremented slowly when the single push button is first depressed, and then advances more rapidly. To set the time, the single push button must be released at the precise moment when the desired time is depicted on the display. If one overshoots, it is necessary to suffer the boredom of keeping the push button depressed while 24 hours blink by on the display in order to make a second attempt at setting the time. One's attention tends to wander during this procedure, and a third or even a fourth attempt may be necessary before the time is finally set.
In more expensive equipment, multiple push buttons using printed wiring contacts may be employed to set the time on the display. For example, if two push buttons are present, one can be used to increment the time depicted on the display and the other can be used to decrement the displayed time if there has been an overshoot. If four push buttons are present, one pair might be used for rapid incrementing and decrementing and the other pair for slow incrementing and decrementing. Even with the flexibility afforded by four push button switches, however, the process of setting the time is time-consuming and frustrating. This is particularly true when a VCR is being programmed with the starting times and ending times of a sequence of television programs which are to be recorded.